Display device and flexible wiring board

ABSTRACT

According to one embodiment, a display device includes a display panel, a case including a bottom plate and a side plate provided on the bottom plate and attached to the display panel, and a flexible wring board including a first end joined to the display panel and extending from the display panel toward the bottom plate while being curved around the side plate. The flexible wring board includes a substrate, a conductive layer on a first surface of the substrate and constituting wires, and a protective layer overlaid on the conductive layer and the substrate and opposed to an outer surface of the case. The flexible wring board includes a curved portion curved along the side plate, and the substrate includes a concavity provided in the curved portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-022321, filed Feb. 9, 2018, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device and aflexible wiring board.

BACKGROUND

Liquid crystal display devices and organic electroluminescent (EL)display devices are widely used as a display device of smartphones,tablet computers, vehicle-navigation systems, etc. For example, liquidcrystal displays comprise a liquid crystal display panel and a backlightdevice which illuminates the liquid crystal display panel. The backlightdevice includes a case (or bezel) attached to the liquid crystal displaypanel, and various optical members accommodated in the case. A driver ICis mounted near an input terminal of the liquid crystal display panel.Further, a flexible printed circuit (FPC) is jointed to the liquidcrystal display panel and is electrically connected to the driver IC.The FPC is extends outward from the liquid crystal display panel and isbent, for example, toward a bottom surface side of the case to be placedalong a side surface and a rear surface of the case.

In recent years, narrowing a frame in display devices is progressing.For example, a driver IC is mounted on an FPC, and thus a driver ICconventionally mounted on a display panel is omitted, thereby achievingthe narrowing the frame of the display panel. An FPC mounted with adriver IC, which is referred to as COF hereinafter, requires to increasethe thickness of a substrate (a sheet-shaped base material, for example,polyimide) to enhance the mechanical strength as a COF. Such COF has aresilience (elastic restoring force) against bending that is strongerthan that of the ordinary FPC without a driver IC. On the other hand, asnarrowing the frame of display devices progresses, steep bending of theCOF is required. Thus, the curvature of the bent portion of the COFbecomes large, and that causes the resilience of the COF to be furtherstronger. Under narrowing the frame of display devices, suppressing suchresilience is required.

SUMMARY

The present application generally relates to a display device and aflexible wiring board.

According to one embodiment, a display device includes a display panel,a case including a bottom plate and a side plate provided on the bottomplate and attached to the display panel, and a flexible wring boardincluding a first end joined to the display panel and extending from thedisplay panel toward the bottom plate while being curved around the sideplate. The flexible wring board includes a substrate, a conductive layeron a first surface of the substrate and constituting wires, and aprotective layer overlaid on the conductive layer and the substrate andopposed to an outer surface of the case. The flexible wring boardincludes a curved portion curved along the side plate, and the substrateincludes a concavity provided in the curved portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a liquid crystal display deviceaccording to a first embodiment from a display surface side.

FIG. 2 is a perspective view showing the liquid crystal display devicefrom a rear surface side.

FIG. 3 is an exploded perspective view of the liquid crystal displaydevice.

FIG. 4 is a cross sectional view showing a light source-side end of theliquid crystal display device taken along line A-A of FIG. 2.

FIG. 5A is a plan view showing a flexible wiring board when developed.

FIG. 5B is a side view showing the flexible wiring board when developed.

FIG. 6 is a side view showing the flexible wiring board when curved.

FIG. 7A is a plan view of a flexible wiring board according to a secondembodiment.

FIG. 7B is a side view of the flexible wiring board according to thesecond embodiment.

FIG. 8 is a side view showing the flexible wiring board according to thesecond embodiment when curved.

FIG. 9A is a plan view of a flexible wiring board according to a thirdembodiment.

FIG. 9B is a side view of the flexible wiring board according to thethird embodiment.

FIG. 10 is a side view showing the flexible wiring board according tothe third embodiment when curved.

FIG. 11A is a plan view of a flexible wiring board according to a fourthembodiment.

FIG. 11B is a side view of the flexible wiring board according to thefourth embodiment.

FIG. 12 is a side view showing a flexible wiring board according to thefourth embodiment when curved.

FIG. 13A is a plan view of a flexible wiring board according to a fifthembodiment.

FIG. 13B is a side view of the flexible wiring board according to thefifth embodiment.

FIG. 14 is a side view showing the flexible wiring board according tothe fifth embodiment when curved.

FIG. 15A is a plan view of a flexible wiring board according to a sixthembodiment.

FIG. 15B is a side view of the flexible wiring board according to thesixth embodiment.

FIG. 16 is a side view showing the flexible wiring board according tothe sixth embodiment when curved.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, adisplay device comprises a display panel; a case comprising a bottomplate opposing a rear surface of the display panel and a side plateprovided on the bottom plate and attached to the display panel; and aflexible wring board including one end joined to the display panel andextending from the display panel toward the bottom plate while beingcurved around the side plate of the case. The flexible wring boardcomprises a sheet-shaped substrate, a conductive layer formed on a firstsurface of the substrate and constituting wires, and a protective layeroverlaid on the conductive layer and the substrate and opposing an outersurface of the case. The flexible wring board includes a curved portioncurved along the side plate, and the substrate comprises a concavityprovided in the curved portion. The concavity comprises a bottom portionprovided closer to the first surface and opened towards a second surfaceof the substrate, which is opposite to the conductive layer through thefirst surface.

The disclosure is merely an example, and proper changes in keeping withthe spirit of the invention, which are easily conceivable by a personwith ordinary skill in the art, come within the scope of the inventionas a matter of course. In addition, in some cases, in order to make thedescription clearer, the widths, thicknesses, shapes, etc., of therespective parts are illustrated schematically in the drawings, ratherthan as an accurate representation of what is implemented. However, suchschematic illustration is merely exemplary, and in no way restricts theinterpretation of the invention. In addition, in the specification anddrawings, the same elements as those described in connection withpreceding drawings are denoted by like reference numbers, and detaileddescription thereof is omitted unless necessary.

First Embodiment

FIG. 1 is a perspective view of a liquid crystal display deviceaccording to the first embodiment from a display surface side. FIG. 2 isa perspective view of the liquid crystal display device from a rearsurface side. FIG. 3 is an exploded perspective view of the liquidcrystal display device. FIG. 4 is a cross sectional view of a lightsource-side end of the liquid crystal display device, taken along lineA-A of FIG. 2.

A liquid crystal display 10 can be used, for example, to be installed invarious kinds of electronic devices such as smart phones, tabletdevices, cellular phones, notebook personal computers, handheld gamemachines, electronic dictionaries, television sets and car-navigationsystems.

As shown in FIGS. 1, 2 and 3, the liquid crystal display 10 comprises anactive-matrix type liquid crystal display panel (display panel) 12, acover panel 14 overlaid on a display surface 12 a, which is one mainsurface of the display panel 12, to cover the entire display surface 12a, and a backlight unit (backlight device) 20 opposed to a rear surface,which is the other main surface of the display panel 12.

As shown in FIGS. 3 and 4, the display panel 12 comprises a firstsubstrate SUB1 of a rectangular-plate shape, a second substrate SUB2 ofa rectangular-plate shape opposed to the first substrate SUB1, and aliquid crystal layer LQ provided between the first substrate SUB1 andthe second substrate SUB2. Each of the first substrate SUB1 and thesecond substrate SUB2 is formed of a transparent insulating substratesuch as a glass plate or resin plate. The peripheral portion of thesecond substrate SUB2 is adhered to the first substrate SUB1 with a sealSE. A polarizer PL2 is adhered to the surface of the second substrateSUB2 and forms the display surface 12 a of the display panel 12. Apolarizer PL1 is adhered to the surface of the first substrate SUB1 (therear surface of the display panel 12).

The display panel 12 has a display area (active region) DA of arectangular shape in a region encircled by the seal SE in a state wherethe display surface 12 a is seen in plan view (the state of viewing thedisplay panel from the normal direction of the surface of the displaypanel, as so will be hereinafter). Images are displayed on the displayarea DA. A rectangular frame area (non-display area) ED is providedaround the display area DA. The display panel 12 has a transmissivedisplay function which displays images in the display area DA byselectively transmitting the light from the back light unit 20 throughthe display area DA.

The cover panel 14 is formed of, for example, a glass or acrylictransparent resin, into a rectangular plate shape. In a peripheralportion of the rear surface of the cover panel 14 (a surface on a sideof the display panel 12 or a surface on an opposite side to the surfaceopposing the user), a frame-shaped light-shielding layer RS is formed.The rear surface (back surface) of the cover panel 14 is adhered ontothe polarizer PL2 of the display panel 12 with a light-transmittingadhesives AD or tacking agent.

As shown in FIGS. 2, 3 and 4, the backlight unit 20 comprises a case 18,a plurality of optical members (not shown) disposed in the case 18, anda light source unit 22 which supplies light entering the opticalmembers. In this embodiment, the case 18 comprises a bottom plate 17 ofa rectangular shape, a plurality of side plates (16 a to 16 d) standingon side edges of the bottom plate 17, and a frame 15 of arectangular-frame shape provided in tight contact with these sideplates. The frame 15 and the side plates constitute a pair of long sideplates 16 a and 16 b extending in the long side direction of the displaypanel 12 and opposing each other, and a pair of short side plates 16 cand 16 d extending in the short side direction of the display panel 12and opposing each other.

The frame 15 and the side plates 16 a to 16 d and bottom plate 17 can beformed integrally as one body each from a resin or metal, or such astructure that one of these is made from a resin and the other is madefrom a metal can be adopted as well. In this embodiment, the bottomplate 17 and the side plates 16 a to 16 d are formed from a metal suchas stainless steel (SUS), and the frame 15 is formed from a resin. Theframe 15 is integrated with the side plates 16 a to 16 d by insertionmolding or the like.

As shown in FIG. 3, the backlight unit 20 comprises a light guide (notshown) disposed in the case 18, an optical sheet OS provided on thelight guide, and a light source unit 22 provided on a side of the lightguide. The light source unit 22 comprises a circuit board 23 extendingalong the side plate 16 d, and a plurality of light sources, forexample, light-emitting diodes (LED) 21 mounted on the circuit board 23.The LEDs 21 emit light entering an incident surface of the light guide.The circuit board 23 comprises a connection end portion 23 c, and theconnection end portion 23 c extends outward from the side plate 16 d.

As shown in FIGS. 3 and 4, the backlight unit 20 comprises adouble-sided tape TP1 having a frame-shape. The double-sided tape TP1 isadhered on the frame 15. An outer circumferential edge of thedouble-sided tape TP1 coincides with an outer circumferential edge ofthe case 18. As shown in FIG. 4, an inner circumferential portion of thedouble-sided tape TP1 is adhered to the polarizer PL1, and an outercircumferential portion is adhered to the first substrate SUB1 whileinterposing a spacer SP1 therebetween. The outer circumferential edge ofthe backlight unit 20 coincides the outer circumference edge of thefirst substrate SUB1 except for the light source side. In the lightsource side, a side edge of the backlight unit 20 is located on aslightly outer side from a side edge of the first substrate SUB1.

As shown in FIGS. 2, 3 and 4, the liquid crystal display 10 comprises aflexible wiring board (, which may be referred to as main flexibleprinted circuit (FPC)) joined to the display panel 12. On one short sideof the first substrate SUB1, an exposed portion which does not overlapthe second substrate SUB2 is provided, and a first end portion of themain FPC30 is joined to an upper surface of the exposed portion. Themain FPC 30 extends outwards from a short side of the display panel 12.The main FPC 30 has a width W1 in the first end portion, which is lessthan a width W2 of the first substrate SUB1. The main FPC 30 extends outin a direction perpendicular to, for example, the short side of thefirst substrate SUB1.

As a signal supply source which supplies signals necessary to drive thedisplay panel 12, the main FPC 30 is provided with a semiconductordevice such as the driver IC 24 mounted thereon. (Note that thestructure in which a driver IC is mounted on an FPC or a flexible wiringboard may be referred to as Chip-On flexible printed circuit (COF).) Asub-FPC 25 is joined to a second end portion of the main FPC 23. On thesub-FPC 25, a capacitor C1, connectors 26 and 27 and the like aremounted.

As shown in FIGS. 2 and 4, the main FPC 30 is folded back along an endedge on the short side of the first substrate SUB1, and overlaid on thebottom plate 17 of the backlight unit 20. With this configuration, thefirst end portion side of the main FPC 30 that is on the display panel12 side constitutes a curved portion 31 curved towards the bottom plate17 side of the case 18 from the short side end of the display panel 12.A portion of the main FPC 30 is adhered onto the bottom plate 17 with adouble-sided tape TP2. The sub-FPC 25 is overlaid on the bottom plate17. The connection end portion 23 c of the light source unit 22 isfolded back along the side plate 16 d of the case 18 and opposed to thebottom plate 17. The connection terminal of the connection end portion23 c is connected to the connector 27 on the sub-FPC 25.

FIGS. 5A and 5B are a plan view and a side view, respectively showingthe main FPC when developed, and FIG. 6 is a side view showing the mainFPC 30 when curved.

As shown in FIGS. 5A and 5B, the main FPC 30 is formed into a belt-shapehaving a width W1, which includes a first side edge 35 a and a secondside edge 35 b opposing parallel to each other. The first and secondside edges 35 a and 35 b may not necessarily be parallel to each other,but one side edge or both may be inclined. The main FPC 30 comprises alayered or sheet-shaped substrate 30 a, a conductive layer 30 b formedon a surface (first surface) of the substrate 30 a and constituting aplurality of wires, contact pads and the like, and a protective layer 30c stacked on the conductive layer 30 b and the substrate 30 a to coverthe conductive layer 30 b. The substrate 30 a and the protective layer30 c are formed from, for example, a synthetic resin such as polyimideor polyurethane, and the conductive layer 30 b is formed from anelectroconductive metal layer, for example, a copper foil. The thicknessof the main FPC 30 may vary from one location to another, but, forexample, a thickness T1 of the substrate 30 a is 35 μm and the thicknessof the entire structure thereof is about 52 μm.

The main FPC 30 includes a concavity CN formed in the other surface(second surface) of the substrate 30 a (the surface on an opposite sideto the conductive layer 30 b). In the embodiment, the concavity CNincludes, for example, a groove 34.

The concavity CN, that is, the groove 34 comprises a bottom surface(bottom portion) on a side of the conductive layer 30 b in the substrate30 a, and is open to the second surface of the substrate 30 a, which isopposite to the conductive layer 30 b. In other words, the concavity CNcomprises a bottom portion provided closer to the first surface andopened towards the second surface of the substrate 30 a, which isopposite to the conductive layer 30 b through the first surface.

The groove 34 linearly extends from the first side edge 35 a to thesecond side edge 35 b. Moreover, the groove 34 extends along a locationof the apex of the curved portion 31, that is, along a central line C1which is the center of the curvature. Here, the central line C1 extendsin a direction perpendicular to the first and second side edges 35 a and35 b. For example, the groove 34 is formed into approximately V-shape incross section. A width W3 of the groove 34 is 25 to 100 μm, and a depthd1 of the groove 34 is adjusted to 10 to 25 μm if needed. In thesubstrate 30 a, the region where the groove 34 is provided is formedthin, and more specifically, the thickness of the substrate 30 a isreduced by a portion equivalent to the depth d1 of the groove 34, toform a thin portion (thin-walled portion) 36 whose thickness is lessthan that of the other regions of the main FPC 30. That is, the thinportion 36 is formed as a region between the bottom surface of thegroove 34 and the first surface of the substrate 30 a. The thickness ofthe thin portion 36 is expressed by (T1-d1), and is about 10 to 25 μm.The thickness of the thin portion 36 is set in consideration of thestrength of the substrate 30 a to such a thickness that the thin portion36 is not cracked even if it is bent.

For example, the groove 34 can be formed by applying UV laser onto thesurface of the substrate 30 a in the atmosphere, to partially remove thesubstrate 30 a or subjecting it to line processing. When using laser, itis naturally possible to process the groove 34 into the main FPC itselfas a single body, or even in a state where the main FPC 30 is built inthe display device.

As shown in FIGS. 4 and 6, the main FPC 30 is folded back on the groove34 and the thin-walled portion 36 as its center, and constitutes acircularly curved portion 31. The main FPC 30 is disposed in a directionthat a protective layer 30 c side thereof opposes outer surfaces of thedisplay panel 12 and the case 18. The protective layer 30C and theconductive layer 30 b are located on an inner circumferential side ofthe curved portion 31, and the substrate 30 a is located on an outercircumferential side of the curved portion 31. The groove 34 and thethin-walled portion 36 of the substrate 30 a extends to the location ofthe apex (peak portion, the central line C1 of the bent portion) of thecurved portion 31.

As shown in FIG. 4, a plurality of connection terminals 30 d, which areformed of a part of the conductive layer 30 b, are formed in the firstend portion of the main FPC 30. By thermo-compressing the first endportion to the first substrate SUB1, the plurality of connectionterminals 30 d are electrically connected to the plurality of wires orterminals of the first substrate SUB1, respectively. The driver IC 24 ismounted on the protective layer 30 c and is electrically connected tothe wires of the main FPC 30 via openings or contact pads (not shown)provided in the protective layer 30 c. On the second end portion of themain FPC 30, a plurality of connection terminals (not shown), which areformed of a part of the conductive layer 30 b, are provided. Bythermo-compressing the second end portion to the sub-FPC 25 (see FIG.3), the plurality of connection terminals are electrically connected tothe sub-FPC 25. As described above, a part of the main FPC 30, that is,the regional portion opposing the bottom plate 17 and adjacent to thecurved portion 31 is adhered to the bottom plate 17 by the double-sidedtape TP2. Thus, the curved portion 31 of the main FPC 30 is held in acurved state.

Note that in view of the actual condition of the remarkably slimmeddisplay device of the recently years, the state discussed in thisembodiment, where the main FPC 23 and the like are curved along the case18 may be regarded to be equivalent to the state where the main FPC 23is bent along the case 18. Therefore, the expression “curvature” used inthis embodiment covers the bent state where an object is bent or folded,and similarly the expression “bending” also covers the curved statewhere an object is curved at such a degree of curvature that it can beas well regarded to be equivalent to “being bent”.

According to the liquid crystal display and the main FPC of the firstembodiment configured as described above, a concavity CN, for example, agroove 34 is formed in the substrate 30 a of the main FPC 30 to preparethe thin portion 36, and further the main FPC 30 is bent on the groove34 and the thin portion 36 as a center, to form the curved portion 31.With the groove 34 and the thin portion 36 as such, the main FPC 30 canbe easily bent, and further the resilience of the main FPC 30 generatedby bending can be reduced. Therefore, the breaking of the joint betweenthe backlight unit 20 and the display panel 12, detachment of thedouble-sided tape TP2, detachment of internal parts of the backlightunit 20, and the like, which may be caused by the resilience of the mainFPC 30 can inhibited, thereby making it possible to improve thereliability of the display device. Further, the main FPC 30 can be benteven more steeply (the main FPC can be bent at a greater curvature), andtherefore the main FPC 30 can be adopted for further thinner displaydevices.

As described above, according to the first embodiment, a display deviceand a flexible wiring board which can improve the reliability and reducethe manufacturing cost can be provided.

Note that in the first embodiment, the liquid crystal display panel 12is used for the display panel of the display device, but the displaypanel is not limited to this. For example, an organic electroluminescentdisplay panel may be used as well. In this case, a backlight unit is notnecessary, and the case 18 can be disposed on a rear surface side of theorganic electroluminescence display panel. Moreover, the groove 34 andthe thin portion 36 of the main FPC 30 are formed into a linear shapewhich extends continuously in its width direction, but the structure isnot limited to this. For example, the groove and the thin portion may beformed into a dashed line shape which extends in the width direction.

Next, a flexible wiring board of a display device according to anotherembodiment will now be described. In other embodiments described below,the same referential marks are given to the same parts as those of thefirst embodiment discussed above, the detailed explanation is omitted orsimplified, and they describes in detail focusing on different partsfrom the first embodiment.

Second Embodiment

FIGS. 7A and 7B are respectively a plan view and a side view showing adeveloped main FPC according to a second embodiment and FIG. 8 is a sideview showing the main FPC when curved, of the second embodiment.

As shown, according to the second embodiment, a groove 34 whichconstitutes a concavity CN of a main FPC 30 extends continuously andlinearly from a first side edge 35 a to a second side edge 36 b. A widthW3 of the groove 34 is greater than the width of the groove 34 in thefirst embodiment. A bottom surface of the groove 34 is formed into acircularly curved surface. A depth d1 of a deepest region of the groove34 is 10 to 25 μm. In a substrate 30 a, a region where the groove 34 isformed by partially removing the substrate 30 a into a thin layer andthus a thin portion (thin-walled portion) 36 which is thinner than theother regions is formed.

For example, the groove 34 is formed by applying UV laser onto a surfaceof the substrate 30 a while maintain the laser out of focus, to removethe substrate 30 a broadly and gently in slope.

In the second embodiment, the other structures of the main FPC 30 arethe same as those of the main FPC 30 of the first embodiment.

According to the second embodiment, the bottom surface of the groove(concavity) 34 is form into an arc shape, and with this structure, whenbending the main FPC 30, concentration of stress on the thin-walledportion 36 can be relaxed. In addition, also in the second embodiment,advantages similar to those of the above-described first embodiment canbe obtained.

Third Embodiment

FIGS. 9A and 9B are respectively a plan view and a side view showing adeveloped main FPC according to a third embodiment, and FIG. 10 is aside view showing the main FPC when curved, of the third embodiment.

As shown according to the third embodiment, a groove 34 whichconstitutes a concavity CN of a main FPC 30 extends continuously andlinearly from a first side edge 35 a to a second side edge 36 b. A widthW3 of the groove 34 is greater than the width of the groove 34 of thefirst embodiment, and the groove 34 has such a width that it extendsover a full length of a curved portion 31 thereof. That is, the groove34 is formed to have a width expand over an entire region of the curvedportion 31 including one end of the curved portion 31 on a display panelside and the other end of the curved portion 31 on a bottom plate sideof the case. In other words, the groove 34 is formed to have a widthexpanded over an entire region of the curved portion 31 including oneend closer to the display panel and the other end closer to the bottomplate of the case. A bottom surface of the groove 34 is formed into aflat surface parallel to the surface of the substrate 30 a. The groove34 has a uniform depth d1 over the entire width W3 of the groove 34 (,which is, for example, 10 to 25 μm).

The groove 34 described above can be formed by etching or O₂-ashing. Forexample, in O₂-ashing, plasma is generated in vacuum and O₂ is made tostrike at the surface of the substrate 30 a to bind carbon in thesubstrate (polyimide) and O₂ together into carbon dioxide to be removed.

In the substrate 30 a, the region where the groove 34 is formed into athin portion by partially removing the substrate 30 a, and thus the thinportion (thin region) 36 layer whose thickness is less than those of theother regions is formed. In this embodiment, the thin portion 36 isformed to extend over an entire length of the curved portion 31. Thethin portion 36 has a uniform layer thickness (T1-d1) over the entireregion thereof.

In the third embodiment, the other structures of the main FPC 30 are thesame as those of the main FPC 30 of the first embodiment.

According to the third embodiment, the entire region of the curvedportion 31 is formed into the thin-walled portion (thin portion) 36, andthus the entire curved portion 31 can be reduced in stiffness and beeasily bendable. Further, the resilience of the main FPC 30, which isgenerated by bending, can be further reduced. Furthermore, the depth d1of the groove 34, or the thickness of the thin portion 36 is madeuniform over the entire region of the curved portion 31, and thusconcentration of stress on the curved portion 31 can be relaxedregardless of the curvature of the curved portion 31. In addition,effects similar to those of the first embodiment can be obtained in thethird embodiment.

Fourth Embodiment

FIGS. 11A and 11B are respectively a plan view and a side view of themain FPC when developed, and FIG. 12 is a side view showing of the mainFPC when curved.

As shown, according to the fourth embodiment, a main FPC 30 comprises,in a curved portion 31, a plurality of grooves 34 formed in a substrate30 a. The plurality of grooves 34 constitute one concavity CN in thesubstrate 30 a. The grooves 34 each extend continuously and linearly ina width direction of the substrate 30 a from a first side edge 35 a to asecond side edge 35 b. Moreover, one groove 34 extends along a locationof the apex of the curved portion 31 (a central line C1 of curvature),that is, along a central line C1 which is the center of the curvature.The other grooves 34 are provided on one or both sides of the apex. Forexample, a width W3 of each groove 34 is 25 to 100 μm, and a depth d1 ofthe groove 34 is 10 to 25 μm. The grooves 34 have the same width W3 anddepth d1. Moreover, the grooves 34 are arranged at a constant pitch P1.The grooves 34 are provided at constant intervals over substantially theentire region of the curved portion 31. Note that the grooves 34 can beformed by, for example, liner processing using UV laser.

In the substrate 30 a, regions where the grooves 34 are provided areformed thin, and more specifically, the thickness is reduced by aportion equivalent to the depth d1 of the grooves 34, to form thinportions (thin-walled portions) 36 whose thickness is less than that ofthe other regions of the main FPC 30. Thus, these thin portions areformed to respectively correspond to the grooves. The grooves 34 and thethin portions 36 are provided at constant interval over the entireregion of the curved portion 31, that is, the entire region of thecurved portion 31 which includes one end of the curved portion 31 on adisplay panel side and the other end on side of a bottom plate of thecase.

In the fourth embodiment, the other structures of the main FPC 30 arethe same as those of the main FPC 30 of the first embodiment.

According to the fourth embodiment, substantially the entire region ofthe curved portion 31 are formed with a concavity CN including thegrooves 34 and the plurality of thin portions 36, and thus the entirecurved portion 31 can be reduced in the stiffness and can be easilybendable. Thus, the resilience of the main FPC 30, which is generated bybending, can be further reduced. Furthermore, with the plurality ofgrooves 34 and thin portions 36 thus provided, the concentration ofstress on the curved portion 31 can be relaxed, thereby making itpossible to improve the durability of the curved portion 31. Inaddition, effects similar to those of the first embodiment can beobtained in the fourth embodiment.

Note that in the fourth embodiment, the width W1 and the depth d1 of thegrooves 34 may not be all the same as each other, but such a structuremay as well be adopted that the width and depth may vary from one grooveto another. The pitch P1 of the grooves 34 is not limited to beconstant, but it may be varied from one location to another.

Fifth Embodiment

FIGS. 13A and 13B are respectively a plan view and a side view of a mainFPC when developed, and FIG. 14 is a side view of the main FPC whencurved.

As shown, according to the fifth embodiment, a substrate 30 a of a mainFPC 30 comprises a concavity CN which includes a plurality of grooves 34formed in a curved portion 31. The grooves 34 each extend continuouslyand linearly in a width direction of the substrate 30 a from a firstside edge 35 a to a second side edge 36 b. Moreover, one groove 34extends along a location of the apex of the curved portion 31. The othergrooves 34 are provided on one or both sides of the apex. For example, awidth W3 of each groove 34 is 25 to 100 μm, and a depth d1 of the groove34 is 10 to 25 μm. The plurality of grooves 34 have the same width W3and depth d1.

The groove 34 is formed along the location of the apex of the curvedportion 31, and a plurality of, for example, two of those formed on bothsides of the groove 34 are provided at a narrow pitch P1. Further, aplurality of, for example, two grooves 34 are provided on each of bothsides of the grooves 34 formed at a pitch P2, which is greater than thepitch P1. For example, the pitch P1 is 0.025 mm and the pitch P2 are 0.1mm.

The plurality of grooves 34 arranged at the pitch P1 are formed so thateach adjacent pair of grooves 34 partially overlap each other. Thus,bottom surfaces of these grooves 34 extend continuously to each other,thus a substantially flat continuous bottom surface is formed. Theplurality of grooves 34 can be formed by, for example, linear processingusing UV laser.

In the substrate 30 a, regions where the grooves 34 are provided areformed thin, and more specifically, the thickness is reduced by aportion equivalent to the depth d1 of the grooves 34, to form thinportions (thin-walled portions) 36 whose thickness is less than that ofthe other regions of the main FPC 30. Thus, these thin-walled portions36 are formed to respectively correspond to the grooves 34. According tothis embodiment, the plurality of grooves 34 provided near the apex ofthe curved portion 31 are formed to partially overlap each other. Withthis structure, the thin-walled portions 36 corresponding to thesegrooves 34 extend to continued to each other, thus forming the widethin-walled portions 36 including the apex.

In the fifth embodiment, the other structures of the main FPC 30 are thesame as those of the main FPC 30 of the first embodiment.

According to the fifth embodiment, substantially the entire region ofthe curved portion 31, that is, the entire region of the curved portion31 from one end of the curved portion 31 on a display panel side to theother end on side of a bottom plate of the case, is formed from theconcavity CN, that is, the grooves 34 and the plurality of thin portions36. Thus the entire curved portion 31 can be reduced in the stiffnessand can be easily bendable. Further, the resilience of the main FPC 30,which is generated by bending, can be further reduced. The thin portions36 are formed to extend over a wide region including the apex of thecurved portion 31, so that the region near the apex of the curvedportion 31 can be made easily bendable. Even when the curved portion 31is bent steeply, the concentration of stress on the vicinity of the apexcan be relaxed. In addition, effects similar to those of the firstembodiment can be obtained in the fifth embodiment.

Sixth Embodiment

FIGS. 15A and 15B are respectively a plan view and a side view of a mainFPC when developed, and FIG. 16 is a side view of the main FPC whencurved.

As shown, according to the fifth embodiment, a substrate 30 a of a mainFPC 30 comprises a plurality of grooves 34 which constitute a concavityCN in a curved portion 31. The grooves 34 each extend continuously in awidth direction of the substrate 30 a from a first side edge 35 a to asecond side edge 35 b. Each groove 34 curves a plurality of timesbetween the second side edge 35 b and the first side edge 35 a. Forexample, each groove 34 is formed into a wave form which curves aplurality of times up and down.

One groove 34 extends along a location of the apex of the curved portion31. The other grooves 34 are provided on both sides of the apex and therest on the other side. The grooves 34 have a width W3 and a depth d1which are the same as each other. The grooves 34 are arranged at aconstant pitch P1. The grooves 34 are provided at a constant intervalover substantially the entire region of the curved portion 31. Note thatthese grooves 34 can be formed by, for example, linear processing usingUV laser.

In the substrate 30 a, regions where the grooves 34 are provided areformed thin, and more specifically, the thickness is reduced by aportion equivalent to the depth d1 of the grooves 34, to form thinportions (thin-walled regions) 36 whose thickness is less than that ofthe other regions of the main FPC 30. Thus, these thin portions 36 areformed to respectively correspond to the grooves 34. The thin portions36 respectively corresponding to the groove 34 s extend to curve aplurality of times into a wave form. The thin portions 36 are arrangedat a constant interval over substantially the entire region of thecurved portion 31.

In the sixth embodiment, the other structures of the main FPC 30 are thesame as those of the main FPC 30 of the first embodiment.

According to the sixth embodiment, substantially the entire region ofthe curved portion 31, that is, the entire region of the curved portion31 including one end of the curved portion 31 on a display panel side toanother end on side of a bottom plate of the case, is formed from theconcavity CN including the grooves 34 and the thin portions 36. Thus theentire curved portion 31 can be reduced in the stiffness and can beeasily bendable. Further, the resilience of the main FPC 30, which isgenerated by bending, can be further reduced. The thin portions 36 eachextend to curve a plurality of times into a wave form, and thus the thinportions 36 extend to overlap the apex (central line C1 of thecurvature) of the curved portion 31. With the plurality of thin portions36, the concentration of stress on the apex of the curved portion 31 canbe relaxed. Therefore, regardless of the curvature of the curved portion31, the concentration of stress on the apex of the curved portion 31 canbe relaxed, and the durability of the curved portion 31 can be improved.

In the sixth embodiment, the form of all the grooves 34 is not limitedto wavy, but such a structure may as well be adopted that some of thegrooves 34 provided in the region including the apex of the curvedportion 31 are formed wavy, whereas others provided in the locationsspaced apart from the apex are formed to extend linear.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

Based on the structures which have been described in the above-providedembodiments and modification, a person having ordinary skill in the artmay achieve structures with arbitral design changes; however, as long asthey fall within the scope and spirit of the present invention, suchstructures are encompassed by the scope of the present invention. Forexample, the structural members of the display panel and the backlightdevice and the outer and inner shapes of the frame are not limited torectangular, but one or both of the outer and inner shapes may be insome other shape, for example, polygonal, circular, elliptical, acombination of any of these or the like when seen in plan view. Thedisplay devices are not limited to a flat shape but may be partially orentirely curved or inclined. The materials of the structural members arenot limited to those of the examples provided above, but may be selectedfrom various options.

In a flexible wiring board, a curved portion may be formed not only inone location, but in a plurality of locations. In other words, such astructure may as well be adopted that a flexible wiring board is bendsat a plurality of locations. In this case, it suffices if a groove(concavity) and a thin portion discussed above is provided in eachcurved portion. Moreover, the angle of the curvature of the curvedportion is not limited to 180 degrees, but it may be set at any otherangle.

In the second to sixth embodiments described above, the grooves 34 andthe thin portions 36 of the main FPC 30 are formed to extend linear orwavy continuously along the width direction, but the form is not limitedto this. For example, the grooves and thin portions may be formed into adashed line manner which extends in the width direction.

Furthermore, regarding the present embodiments, any advantage and effectthose will be obvious from the description of the specification orarbitrarily conceived by a skilled person are naturally consideredachievable by the present invention.

What is claimed is:
 1. A display device comprising: a display panel; acase comprising a bottom plate opposing a rear surface of the displaypanel and a side plate provided on the bottom plate and attached to thedisplay panel; and a flexible wring board including one end joined tothe display panel and extending from the display panel toward the bottomplate while being curved around the side plate of the case, the flexiblewring board comprising a sheet-shaped substrate, a conductive layerformed on a first surface of the substrate and constituting wires, and aprotective layer overlaid on the conductive layer and the substrate andopposing an outer surface of the case, the flexible wring boardincluding a curved portion curved along the side plate, and thesubstrate comprising a concavity provided in the curved portion, theconcavity comprising a bottom portion provided closer to the firstsurface and opened towards a second surface of the substrate, which isopposite to the conductive layer through the first surface.
 2. Thedisplay device of claim 1, wherein the flexible wring board including afirst side edge and a second side edge, extending in a curving directionof the curved portion, and the concavity is provided from the first sideedge to the second side edge.
 3. The display device of claim 2, whereinthe concavity comprises one or a plurality of grooves having a crosssection of a circular shape or V-shape, formed in the second surface onan opposite side to the conductive layer.
 4. The display device of claim3, wherein the grooves extend linearly from the first side edge to thesecond side edge in the curved portion.
 5. The display device of claim3, wherein the grooves extend from the first side edge to the secondside edge in a wave form in the curved portion, and at least a part ofthe grooves overlaps a central portion of curvature of the curvedportion.
 6. The display device of claim 1, wherein the curved portionincludes a first end on a side of the display panel and a second end ona side of the case in the flexible wring board, and the concavity has awidth over an entire region of the curved portion, which includes thefirst and second ends, and the bottom portion is formed flatly.
 7. Thedisplay device of claim 1, wherein the concavity comprises one or aplurality of grooves extending in a direction which intersects a curvingdirection of the curved portion.
 8. The display device of claim 7,wherein the grooves are arranged in the curving direction at a constantpitch.
 9. The display device of claim 7, wherein a first group ofgrooves, which includes the one groove, are arranged at a first pitch,and a second group of grooves, which are located on both sides of thefirst group, are arranged at a second pitch which is greater than thefirst pitch.
 10. A flexible wiring board comprising: a sheet-shapedsubstrate; a conductive layer formed on a first surface of the substrateand constituting wires; and a protective layer overlaid on theconductive layer and the substrate, the flexible wiring board beingbendable to form a curved portion, and the substrate comprising aconcavity provided in a position corresponding to the curved portion.11. The wiring board of claim 10, further comprising a first side edgeand a second side edge extending to oppose each other, wherein theconcavity comprises a groove provided from the first side edge to thesecond side edge in the curved portion.
 12. The wiring board of claim11, wherein the substrate comprises one or a plurality of grooves formedin a second surface on an opposite side to the conductive layer andconstituting the concavity, and a thin portion whose thickness is lessthan those of other regions of the substrate, which is formed between abottom of the one or plurality of grooves and the first surface of thesubstrate.